Hello, so sorry to hear that, why not backup all of your files on iPhone ?  in my experience, try t o logo in your iTunes account , and check the recover mode. maybe it an recover your lost files. you can also use some other app to recover deleted files. 

Here is tips: how to transfer photos from iPhone to computer . with iStonsoft iPhone to computer transfer app.

One advantage of the iPhone family is that they tend to retain their value to a greater degree than many other mobile devices.  I would also think that selling it right now would maximize your cost recovery, before the new iPhone is released.  Of course, you might be without a device for a little while.  

You could always go the ebay route, but you have to deal with potentially flakey buyers, potential payment issues, and the delay of the auction period.  I stopped selling anything personally on ebay last year when PayPal decided to retain my funds for 30 days after receipt for no clear reason, so be aware that there is the possibility that PayPal will just keep your money and there is almost nothing you can do about it. 

The first poster probably suggested the easiest, quickest and safest way to fund you new iPhone by going through the Apple program, but probably not the most lucrative.  There are other options too, that you should consider.  Check out Gazelle and NextWorth to see how much they will pay you.  They are established companies that let you see how much they will pay before you commit to selling.  Just be honest about the condition of your phone, because if they evaluate it and find the condition is not what you said they will revise the purchase offer downward.   

To get an idea of current value, I just checked on nextworth.com and found they would pay $155 for a functioning black iPhone 4 16GB.  Gazelle.com would pay $146 for the same device in average condition.